The present invention relates to an apparatus for controlling lubrication in an input clutch used in an automatic transmission, and specifically, to an apparatus for controlling lubrication in an electromagnetic input clutch.
In general, an automatic transmission of a continuously variable type (stepless transmission) or a non-continuously variable type (stepwise transmission) is so constructed as to receive rotation of an engine as a power source via a torque converter. The torque converter transmits the power between input and output elements by hydrodynamic force. The torque converter can perform smooth transmission of the power, but there will occur slippage between the input and output elements, causing decrease in fuel economy.
In order to eliminate the above-described disadvantage, there have been proposed automatic transmissions in which an input clutch constituted by an electromagnetic clutch or multiple-disc clutch is used in place of a torque converter. Japanese Patent Applications First Publications Nos. 10-78052 and 5-149418 disclose an automatic transmission including a multiple-disc clutch substituted for a torque converter. The multiple-disc clutch has a relatively large size, and requires such a complicated hydraulic circuit for controlling the clutch application as described in the latter of the earlier techniques. This results in enlarged size and complicated construction of the automatic transmission. In addition, if the multiple-disc clutch is substituted for the torque converter in the automatic transmission, a large change of the design of the automatic transmission must be required. Therefore, it is preferable to use the electromagnetic clutch rather than the multiple-disc clutch.
However, even when the electromagnetic clutch is used for the input clutch, it is required to apply the input clutch at a slipping state in order to prevent undesired shock from being caused upon the starting or speed-change operation of the automatic transmission. Accordingly, the electromagnetic input clutch must be lubricated.
The lubrication circuit of the electromagnetic input clutch includes an oil pump for pumping a lubricating oil from an oil source. The oil pump is disposed at the connection between a transmission casing and an input clutch housing. A control valve body is mounted to a lower portion of the transmission casing and adapted to control speed-change of the automatic transmission using the oil fed from the oil pump as a working medium. An excessive oil from the control valve body is utilized for lubricating the electromagnetic input clutch within the input clutch housing. The lubricating oil to be used for lubrication of the electromagnetic input clutch must be supplied from the central portion of the input clutch because the input clutch per se is a rotor. Therefore, the lubrication circuit cannot be formed at the outer periphery of the input clutch. For the reasons described above, the formation of the lubrication circuit tends to increase diameter of a transmission input shaft and radial dimension of the entire automatic transmission.
Further, if two lubrication circuits for the input clutch are arranged parallel to each other and selectively used for easy control of an amount of the lubricating oil, the above-described tendency will become more significant. There is a demand for providing the solution of the above problem.
An object of the present invention is to provide an apparatus for controlling lubrication in an input clutch of an automatic transmission, which is provided with two parallel lubrication circuits for the input clutch without increasing radial dimensions of a transmission input shaft and the automatic transmission and is capable of readily controlling an amount of a lubricating oil to be used for lubrication in the input clutch.
A further object of the present invention is to provide an apparatus for lubricating an electromagnetic input clutch of an automatic transmission, which is capable of being constructed without substantially changing the design of the automatic transmission utilizing a torque converter.
According to one aspect of the present invention, there is provided an input clutch lubrication control apparatus for au automatic transmission, comprising:
an oil pump discharging a lubricating oil;
a sleeve;
an input shaft having an axial bore, the input shaft rotatably supported by the sleeve;
an electromagnetic input clutch electromagnetically operated to be drivingly coupled with the input shaft upon being applied;
a first lubrication circuit feeding the lubricating oil discharged from the oil pump to the electromagnetic input clutch, the first lubrication circuit including a space between an outer circumferential surface of the input shaft and an inner circumferential surface of the sleeve; and
a second lubrication circuit feeding the lubricating oil discharged from the oil pump to the electromagnetic input clutch, the second lubrication circuit including the axial bore of the input shaft; and
a controller programmed to control the first and second lubrication circuits to regulate an amount of the lubricating oil fed to the electromagnetic input clutch.
According to a further aspect of the present invention, there is provided an input clutch lubrication control apparatus for au automatic transmission, comprising:
an oil pump discharging a lubricating oil;
a sleeve;
an input shaft rotatably received by the sleeve with a space therebetween, the input shaft having an axial bore;
an electromagnetic input clutch electromagnetically operated to be drivingly coupled with the input shaft upon being applied;
first lubrication passage means for fluidly communicating the electromagnetic input clutch with the oil pump through the space between the sleeve and the input shaft;
second lubrication passage means for fluidly communicating the electromagnetic input clutch with the oil pump through the axial bore of the input shaft; and
a controller programmed to control the first and second lubrication passage means depending on an operating state of the electromagnetic input clutch.
According to a still further aspect of the present invention, there is provided an automatic transmission, comprising:
an oil pump discharging a lubricating oil;
a sleeve;
an input shaft rotatably supported by the sleeve;
an electromagnetic input clutch electromagnetically operated to be drivingly coupled with the input shaft upon being applied;
first and second lubrication circuits fluidly communicating the electromagnetic input clutch with the oil pump and arranged parallel to each other; and
a controller programmed to perform either one of a mono-circuit lubrication control in which the first lubrication circuit is used and a bi-circuit lubrication control in which the first and second lubrication circuits are used, depending on an operating state of the electromagnetic input clutch.